The invention relates to a bioerodible contraceptive device, and, more particularly, to an intravaginally-dissolvable contraceptive suppository comprising a lyophilized foam and a contraceptive, a method of using such suppositories and a method for manufacturing them.
Vaginal contraceptives are well-known in the art, including, for example, spermicidal creams and gels. These products can be used alone or in conjunction with removable contraceptive devices, such as intrauterine devices. Although many of these products are readily available without a prescription, there are several disadvantages associated with their use. The effectiveness of these products is generally limited to one or two hours. In addition, these creams or gels tend to melt very readily and, thus, are easily discharged from the vagina, thereby further limiting their effectiveness. Furthermore, the tendency to rapidly melt makes such products inconvenient and messy to use.
In the area of foams, although the use of foams and freeze-dried foams to deliver various active ingredients is well-known, such foams generally do not possess the requisite characteristics that would render them suitable for use as a contraceptive suppository. For example, in U.S. Pat. No. 4,642,903, Davies discloses the use of freeze-dried foams for dispensing a variety of active ingredients. However, Davis' foams are designed to have very rapid dissolution rates (virtually instantaneous) which would render his foam highly ineffective for use as a contraceptive. Moreover, it is not possible to control the degree of aeration in Davis' foaming process; accordingly, using Davis' method it is not possible to control densities, dosage delivery rates and dissolution times of the foams which is critical to the manufacture of a contraceptive suppository.
Similarly, in U.S. Pat. No. 4,292,972, Pawelchak et al. discloses a lyophilized foam sponge product containing sodium carboxymethylcellulose, pectin, gelatin and a pharmaceutical, that is intended primarily for use as a hemostatic agent. Unfortunately, Pawelchak's dispersions do not aerate readily; therefore, Pawelchak's freeze-dried foams possess poor structural integrity and dissolve too quickly.
Accordingly, a need exists for a bioerodible vaginal contraceptive suppository that, provides for the sustained and/or controlled release of a contraceptive, gives effective protection against pregnancy for at least several hours, and which is not readily expelled. In addition, there is a need for a method of manufacturing such suppositories whereby the dissolution time and the drug delivery rate of the suppository can be substantially controlled and readily reproduced.